This invention relates to an authenticatable security paper and authenticating composition which together constitute a security paper authenticating system. The invention also extends to the method of authenticating the security paper using the authenticating composition, and to the authenticating composition itself.
By a "security paper" is meant any paper having a value such as to render it potentially liable to attempts at counterfeiting. Typical examples of such papers are papers as conventionally used in security documents, for example: cheques; travellers cheques; money orders; bankers drafts; bearer bonds; share certificates and other certificates; stamps; postal orders; identify documents; registration documents; driving licences, vehicle road tax licences and other licences or permits; electoral papers; savings or bank account passbooks; passports; lottery tickets; admission tickets; travel tickets; vouchers; coupons; tokens; and shipping and other transport documents; in banknotes; and as the signature panels for credit cards, cheque guarantee cards, bank cards or identity cards.
It is desirable that the authenticity of the paper used in at least certain types of security document should be easily verifiable by people to whom such documents may be presented, for example a clerk at a bank, post office or airline check-in counter, or a ticket collector at a sports stadium, theatre or other auditorium. Such verification must be quick and easy, and not necessarily reliant on sophisticated equipment of the kind only available in a laboratory. Desirably, however, the authenticating system should also be capable of use in an automatic verification system, for example involving an inking mechanism followed by an optical image detector.
Papers for use in labels or distinctive packaging may also be subject to counterfeiting particularly if they bear a manufacturer's name and/or a brand name. Considerable publicity has been given in recent years to the problems of illegal marketing of cheap copies of branded goods, for example car brake pads, and prestigious brands of wristwatch or clothing, and of illegal copying of pre-recorded music cassettes, records or videotapes or of computer programs. The copies are liable to be packaged and branded in much the same way as genuine goods from an original or authorised manufacturer. Thus the use of verifiable or authenticatable paper in the labels and/or packaging of the goods provides a means of checking the authenticity of branded goods. Verifiable or authenticatable label or packaging paper is therefore within the ambit of the term "security paper" as used in this specification.
It has previously been proposed to meet the above-described need for easy manual verification by incorporating in the paper a chemical reagent which on being contacted by an authenticating composition will produce a characteristic colour (or colour change). The authenticating composition may be applied, for example, by means of a pen or a stamp pad. Examples of proposals of this nature may be found in U.S. Pat. Nos. 3,001,887 and 3,523,866 and British Pat. No. 1,507,454.
Numerous colour-generating or colour-changing reactions are known, and potentially therefore, there are a large number of colour-generating or colour-changing authenticating systems available for use with security papers as described above. In practice however, very few such systems have been commercialized. The reasons for this are thought to be one or more of the following:
the colour-generating or -changing reaction is too slow or will not take place at all in the medium of a sheet of paper;
the chemicals involved are unacceptable for safety or environmental reasons;
the chemicals involved are too costly for the authenticating system to be economic;
the chemical required to be incorporated in the paper adversely affects the colour or appearance of the paper, either because the chemical is itself coloured or because it discolours with time;
the chemical required to be incorporated in the paper is incompatible with normal papermaking chemicals (e.g. alum, sizing agents, or retention aids);
the colour-generating reaction is dependent on precisely controlled or extreme reaction conditions which are not readily achievable in practice; and
the colour generated by the authenticating reaction is aesthetically unappealing.
It is an object of the present invention to provide an improved security paper authenticating system which both facilitates easy authentication by either manual or automatic means and avoids or minimises the above-described drawbacks.
We have now discovered that the above object can be achieved by incorporating starch and an iodate salt, preferably potassium iodate, in the paper and using an acidic solution of an iodide salt, preferably potassium iodide, as the authenticating composition, preferably with a reducing antioxidant also present. Iodine is liberated on contact of the iodate salt and the acidic iodide salt, according to the following reaction: EQU IO.sub.3.sup.- +5I.sup.- +6H.sup.+ =3I.sub.2 +3H.sub.2 O (1)
The liberated iodine reacts immediately with the starch to produce the characteristic starch-iodine dark blue/black colouration.
The use of iodate and iodide salts in combination for the generation of iodine for security purposes is not novel in itself, having been proposed in patents dating from the last century, namely British Patent No. 748 of 1891 and U.S. Pat. No. 302,758, issued in 1884. In both these cases however, iodate and iodide salts, and starch (together with other chemicals) were all proposed to be incorporated in the paper together, as a means of revealing attempts at fraudulent alteration of security documents by means of acids, bleaching fluids or alkalies. Fraudulent alteration with at least certain of these agents would result in liberation of iodine, and hence in the characteristic starch-iodine colouration.
The use of iodate salt (other than in combination with iodide salt) is known for the detection of attempts at fraudulent alteration using proprietary ink eradicators. These typically use reducing agents such as sodium metabisulphite. The reducing agent reduces the iodate to iodine and so produces the starch-iodine colouration on contact with starch also present in the paper.
The use of iodide salt (other than in combination with iodate salt) has also been proposed in a number of early patents, again for the detection of attempts at fraudulent alteration. These patents include British Pat. Nos. 13521 of 1851; 1386 of 1856; 7206 of 1909; and 2075 of 1911; and U.S. Pat. Nos. 531,507; 1,269,863; and 2,123,597.
The present invention is to be contrasted with these earlier proposals in that whereas the iodate and starch are present in the paper, the iodide is added only for authentication purposes. Such authentication of the paper used in a security document is to be contrasted and distinguished from the detection of attempts at fraudulent alteration of material written or printed on security documents using authentic security paper.
Accordingly, the present invention provides in a first aspect a security paper authenticating system comprising, in combination, a security paper carrying both starch and an iodate salt, and an authenticating composition comprising an acidic solution of an iodide salt, the system being such that on applying the authenticating composition to authentic security paper, iodine is generated and a characteristic starch-iodine colouration is produced.
In a second aspect, the present invention provides a method of authenticating a security paper presumed to carry both starch and an iodate salt, wherein an authenticating composition comprising an acidic solution of an iodide salt is applied to the paper, thereby to generate iodine and produce a characteristic starch-iodine colouration if the paper is authentic.
In a third aspect, the present invention provides an authenticating composition for authenticating a security paper presumed to carry both starch and an iodate salt, said composition comprising an acidic solution of an iodide salt, whereby on applying the authenticating composition to the paper, iodine is generated and a characteristic starch-iodine colouration is produced.